1. Field of the Invention
The present invention relates generally to cementitious compositions and methods of using such compositions, and more particularly, to cementitious compositions containing drilling fluid and methods of using such compositions in performing well cementing operations.
2. Description of the Prior Art
A variety of drilling fluids are used in drilling wells such as oil, gas and water wells. The most commonly used drilling fluids are solids-containing water base gels which can be weighted with particulate weighting materials such as barite. After a well bore is drilled during which the drilling fluid used is circulated through the well bore, the circulation of the drilling fluid is stopped while the well is logged and a string of pipe, e.g., casing, is run in the well bore. After the pipe is run, the drilling fluid in the well bore is conditioned by circulating drilling fluid downwardly through the interior of the pipe and upwardly through the annulus between the exterior of the pipe and the walls of the well bore while removing drilling solids and gas therefrom.
The next operation performed on the well is usually primary cementing, i.e., the string of pipe disposed in the well bore is cemented therein by placing a cementing composition in the annulus between the pipe and the walls of the well bore. The cementing composition is permitted to set into a hard substantially impermeable mass in the annulus whereby the pipe is bonded to the walls of the well bore and the annulus is sealed. When the cementing composition is run down the pipe and into the annulus, the drilling fluid in the pipe and annulus is displaced therefrom. The used drilling fluid is generally accumulated in a pit or tank and then disposed of.
The disposal of drilling fluid is time consuming and expensive, particularly in offshore drilling locations, in that drilling fluid often must be disposed of as a fluid which is hazardous to the environment. Thus, any environmentally safe use to which all or part of the drilling fluid can be put at a well site is highly advantageous since it eliminates the need for disposing of all or part of the drilling fluid.
By the present invention, improved cementitious compositions and methods of using such compositions in well cementing operations are provided. A portion of the drilling fluid used to drill a well can be utilized as a component in the cementitious composition used for cementing the well. The portion of the drilling fluid which is not utilized in the cementing composition can be disposed of conventionally, or it can be incorporated into a cementitious composition of this invention, placed into an environmentally safe location and allowed to set into a hard environmentally safe cementitious mass therein.